LSP Setup for GitHub Copilot CLI

UTILITY SKILL — installs and configures Language Server Protocol servers for Copilot CLI. USE FOR: "setup LSP", "install language server", "configure LSP for Java", "add TypeScript LSP", "enable code intelligence", "I need go-to-definition", "find references not working", "need better code understanding" DO NOT USE FOR: general coding tasks, IDE/editor LSP configuration, non-Copilot-CLI setups

Workflow

1. Ask the language — use

   ask_user

   to ask which programming language(s) the user wants LSP support for
2. Detect the OS — run

   uname -s

   (or check for Windows via

   $env:OS

   /

   %OS%

   ) to determine macOS, Linux, or Windows
3. Look up the LSP server — read

   references/lsp-servers.md

   for known servers, install commands, and config snippets
4. Ask scope — use

   ask_user

   to ask whether the config should be user-level (

   ~/.copilot/lsp-config.json

   ) or repo-level (

   lsp.json

   at the repo root or

   .github/lsp.json

   )
5. Install the server — run the appropriate install command for the detected OS
6. Write the config — merge the new server entry into the chosen config file (

   ~/.copilot/lsp-config.json

   for user-level;

   lsp.json

   or

   .github/lsp.json

   for repo-level). If a repo-level config already exists, keep using that location; otherwise ask the user which repo-level location they prefer. Create the file if missing and preserve existing entries.
7. Verify — confirm the LSP binary is on

   $PATH

   and the config file is valid JSON

Configuration Format

Copilot CLI reads LSP configuration from user-level or repo-level locations, and repo-level config takes precedence over user-level config:

• User-level:

  ~/.copilot/lsp-config.json

• Repo-level:

  lsp.json

  (repo root) or

  .github/lsp.json

The JSON structure:

{
  "lspServers": {
    "<server-key>": {
      "command": "<binary>",
      "args": ["--stdio"],
      "fileExtensions": {
        ".<ext>": "<languageId>",
        ".<ext2>": "<languageId>"
      }
    }
  }
}

Key rules

• command

  is the binary name (must be on

  $PATH

  ) or an absolute path.

• args

  almost always includes

  "--stdio"

  to use standard I/O transport.

• fileExtensions

  maps each file extension (with leading dot) to a Language ID.
• Multiple servers can coexist in

  lspServers

  .
• When merging into an existing file, never overwrite other server entries — only add or update the target language key.

Behavior

• Always use

  ask_user

  with

  choices

  when asking the user to pick a language or scope.
• If the language is not listed in

  references/lsp-servers.md

  , search the web for "<language> LSP server" and guide the user through manual configuration.
• If a package manager is not available (e.g. no Homebrew on macOS), suggest alternative install methods from the reference file.
• After installation, run

  which <binary>

  (or

  where.exe

  on Windows) to confirm the binary is accessible.
• Show the user the final config JSON before writing it.
• If the config file already exists, read it first and merge — do not clobber.

Verification

After setup, tell the user:

1. Type

   /exit

   to quit Copilot CLI — this is required so the new LSP configuration is loaded on next launch
2. Re-launch

   copilot

   in a project with files of the configured language
3. Run

   /lsp

   to check the server status
4. Try code intelligence features like go-to-definition or hover